# finding fourier series

• September 23rd 2008, 09:12 AM
panda
finding fourier series
f(x) = -1 for -pi<x<o and f(x)= 1 for 0<x<pi

i have b(n) = 4/n.pi
but i wasnt sure how to use this to write it as fourier series.
• September 23rd 2008, 09:32 AM
CaptainBlack
Quote:

Originally Posted by panda
f(x) = -1 for -pi<x<o and f(x)= 1 for 0<x<pi

i have b(n) = 4/n.pi
but i wasnt sure how to use this to write it as fourier series.

Assuming you have the $b$'s right:

$f(x)=\sum_{n=1}^{\infty} b(n) \sin(nx) = \sum_{n=1}^{\infty} \frac{4 \pi}{n} \sin(nx)$

subject to the usual restrictions on $x$

RonL